1. Field of the Invention
The present invention relates to the delivery of media data in a group communications service. In particular, the present invention relates to methods and apparatus for controlling the delivery of media data to a plurality of target devices in a target network.
2. Description of the Related Technology
Various group communications systems allow media data to be delivered from one point in a network to more than one other point in a network. An example of such is a group paging service in which a user of a source device delivers media data to a plurality of target devices. An example application of such group paging services may involve delivery of an announcement from one user of the system to a number of other users of the system.
The term ‘group paging’ as used herein describes a communications system function whereby a paging party having a paging device can transmit an announcement to a set of target devices. A group paging service may be implemented using a variety of mechanisms. For example, a paging party may press a button on a paging device and speak into a microphone. Alternatively, where the paging device is a telephone, the paging party may pick up a telephone, dial an extension, and then speak into a microphone in the telephone handset. In any case, the system may be set up so that the paging party's voice is output through a number of target device loudspeakers around the paging system premises. Typically, the target devices include telephone devices and the audio output loudspeakers are built into the telephone devices.
Depending on the sophistication of the group paging system, multiple “zones” may be supported. A zone represents a predetermined set of target devices in a group communications service such as group paging. Zones may overlap (so a target device may be in more than one zone). When zones are used, the paging party may either specify the zone by the extension number dialed, or the paging device may subsequently prompt for a zone code to be entered after an initial extension number for group paging services is dialed.
In legacy telephone systems, group paging is typically provided by dedicated group paging apparatus connected to a Private Branch Exchange (PBX) in a customer premises telephone switching network, or an equivalent system. Dialing an extension number for group paging services then results in the paging party connecting to the legacy paging apparatus.
It is known to connect legacy group paging apparatus to a hosted packet-based Central Exchange (‘Centrex’) or PBX systems, however in this case there is no on-premises PBX to interface to the legacy paging apparatus. Several attempts have been made to tackle this problem, including both premises-based and host-based approaches.
A premises-based approach requires the use of a further apparatus, such as a gateway adaptor entity, which is deployed at the customer premises to interface to the legacy paging apparatus. The gateway adaptor entity connects to the paging apparatus and may communicate with it for example using a Plain Old Telephone Service (POTS) via a Foreign Exchange Office (FXO) and Foreign Exchange Station (FXS) interface pair, or using packet-based communications and a signaling protocol such as the Session Initiation Protocol (SIP). Just as in the PBX case, the paging party dials an extension number for paging services, and is connected to the paging apparatus, with the option to then enter a zone code to initiate paging. The premises-based approach has the advantages that it re-uses the existing legacy paging apparatus and uses relatively low bandwidth to and from the customer premises. However, the premises-based approach has the disadvantages that it requires an additional piece of apparatus (the gateway adaptor entity) located at the customer premises, and also suffers in that multiple pieces of apparatus must be managed and maintained at multiple locations, without any common look and feel.
A host-based approach can be implemented using a softswitch telephone system located in a remote access network such as the Internet. The softswitch telephone system hosts paging functionality remotely, and can work in conjunction with SIP telephone handsets and loudspeakers to provide paging services. For example, when a paging party dials an extension to access paging services, their paging device connects to the softswitch telephone system and the paging party is prompted to enter a zone code. To deliver paging media data, the softswitch telephone system sets up calls to each target device in the zone, such as one or more SIP telephone speakers and/or SIP-enabled loudspeakers which are configured to be in the zone.
The host-based approach has the advantages that the paging intelligence is hosted on the softswitch, along with other hosted packet-based Centrex and PBX functionality. Management of the paging services functionality can thus be integrated with the management of the other features, meaning consistency for the end-user, and in many cases, no extra customer premises equipment is needed over and above the SIP devices which may already be present. However, the host-based approach has the disadvantage that the paging service can use up valuable bandwidth resources to and from the customer premises. Bandwidth can be limited due, in particular, to bandwidth limitations on the communications link between the customer premises and the remote access network. It would therefore be desirable to provide media data delivery services without at least some of the drawbacks of the prior art.